Add the ability to follow the agent as it makes edits (#29839)

Nathan here: I also tacked on a bunch of UI refinement.

Release Notes:

- Introduced the ability to follow the agent around as it reads and
edits files.

---------

Co-authored-by: Nathan Sobo <nathan@zed.dev>
Co-authored-by: Max Brunsfeld <maxbrunsfeld@gmail.com>

crates/assistant_tool/src/action_log.rs

@@ -29,6 +29,10 @@ impl ActionLog {
         }
     }
 
+    pub fn project(&self) -> &Entity<Project> {
+        &self.project
+    }
+
     /// Notifies a diagnostics check
     pub fn checked_project_diagnostics(&mut self) {
         self.edited_since_project_diagnostics_check = false;